Remove unsafe code from SmtpReplyReaderFactory.ProcessRead by Copilot · Pull Request #121297 · dotnet/runtime

Copilot · 2025-11-03T14:17:18Z

The ProcessRead method used unnecessary unsafe pointer arithmetic despite accepting a ReadOnlySpan<byte> parameter that already provides safe, efficient indexing.

Changes

Replaced unsafe pointer arithmetic with ReadOnlySpan indexing
- Removed unsafe block and fixed statement
- Replaced byte* pointers with integer index tracking
- Changed *ptr++ to buffer[i++], (int)(ptr - start) to i
Fixed pre-existing validation bug (discovered during refactoring)
- Changed if (b < '0' && b > '9') to if (b < '0' || b > '9') in digit validation
- Original condition could never be true (no byte can be both < 48 and > 57)

Before/After

// Before
unsafe {
    fixed (byte* pBuffer = buffer) {
        byte* ptr = pBuffer;
        byte b = *ptr++;
        if (b < '0' && b > '9')  // Bug: never true
            throw new FormatException(...);
    }
}

// After
int i = 0;
byte b = buffer[i++];
if (b < '0' || b > '9')  // Correct validation
    throw new FormatException(...);

All existing tests pass. No API or behavior changes.

Warning

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- Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig System.Net.Mail.Functional.Tests.runtimeconfig.json --depsfile System.Net.Mail.Functional.Tests.deps.json /home/REDACTED/.nuget/packages/microsoft.dotnet.xunitconsoleREDACTED/2.9.3-beta.25528.108/build/../tools/net/xunit.console.dll System.Net.Mail.Functional.Tests.dll -xml testResults.xml -nologo -notrait category=OuterLoop -notrait category=failing (dns block)
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- Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig System.Net.Mail.Functional.Tests.runtimeconfig.json --depsfile System.Net.Mail.Functional.Tests.deps.json /home/REDACTED/.nuget/packages/microsoft.dotnet.xunitconsoleREDACTED/2.9.3-beta.25528.108/build/../tools/net/xunit.console.dll System.Net.Mail.Functional.Tests.dll -xml testResults.xml -nologo -notrait category=OuterLoop -notrait category=failing (dns block)
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- Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig System.Net.Mail.Functional.Tests.runtimeconfig.json --depsfile System.Net.Mail.Functional.Tests.deps.json /home/REDACTED/.nuget/packages/microsoft.dotnet.xunitconsoleREDACTED/2.9.3-beta.25528.108/build/../tools/net/xunit.console.dll System.Net.Mail.Functional.Tests.dll -xml testResults.xml -nologo -notrait category=OuterLoop -notrait category=failing (dns block)
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- Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig System.Net.Mail.Functional.Tests.runtimeconfig.json --depsfile System.Net.Mail.Functional.Tests.deps.json /home/REDACTED/.nuget/packages/microsoft.dotnet.xunitconsoleREDACTED/2.9.3-beta.25528.108/build/../tools/net/xunit.console.dll System.Net.Mail.Functional.Tests.dll -xml testResults.xml -nologo -notrait category=OuterLoop -notrait category=failing (dns block)
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- Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig System.Net.Mail.Functional.Tests.runtimeconfig.json --depsfile System.Net.Mail.Functional.Tests.deps.json /home/REDACTED/.nuget/packages/microsoft.dotnet.xunitconsoleREDACTED/2.9.3-beta.25528.108/build/../tools/net/xunit.console.dll System.Net.Mail.Functional.Tests.dll -xml testResults.xml -nologo -notrait category=OuterLoop -notrait category=failing (dns block)
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- Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig System.Net.Mail.Functional.Tests.runtimeconfig.json --depsfile System.Net.Mail.Functional.Tests.deps.json /home/REDACTED/.nuget/packages/microsoft.dotnet.xunitconsoleREDACTED/2.9.3-beta.25528.108/build/../tools/net/xunit.console.dll System.Net.Mail.Functional.Tests.dll -xml testResults.xml -nologo -notrait category=OuterLoop -notrait category=failing (dns block)
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- Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig System.Net.Mail.Functional.Tests.runtimeconfig.json --depsfile System.Net.Mail.Functional.Tests.deps.json /home/REDACTED/.nuget/packages/microsoft.dotnet.xunitconsoleREDACTED/2.9.3-beta.25528.108/build/../tools/net/xunit.console.dll System.Net.Mail.Functional.Tests.dll -xml testResults.xml -nologo -notrait category=OuterLoop -notrait category=failing (dns block)
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- Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig System.Net.Mail.Functional.Tests.runtimeconfig.json --depsfile System.Net.Mail.Functional.Tests.deps.json /home/REDACTED/.nuget/packages/microsoft.dotnet.xunitconsoleREDACTED/2.9.3-beta.25528.108/build/../tools/net/xunit.console.dll System.Net.Mail.Functional.Tests.dll -xml testResults.xml -nologo -notrait category=OuterLoop -notrait category=failing (dns block)
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- Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig System.Net.Mail.Functional.Tests.runtimeconfig.json --depsfile System.Net.Mail.Functional.Tests.deps.json /home/REDACTED/.nuget/packages/microsoft.dotnet.xunitconsoleREDACTED/2.9.3-beta.25528.108/build/../tools/net/xunit.console.dll System.Net.Mail.Functional.Tests.dll -xml testResults.xml -nologo -notrait category=OuterLoop -notrait category=failing (dns block)
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- Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig System.Net.Mail.Functional.Tests.runtimeconfig.json --depsfile System.Net.Mail.Functional.Tests.deps.json /home/REDACTED/.nuget/packages/microsoft.dotnet.xunitconsoleREDACTED/2.9.3-beta.25528.108/build/../tools/net/xunit.console.dll System.Net.Mail.Functional.Tests.dll -xml testResults.xml -nologo -notrait category=OuterLoop -notrait category=failing (dns block)
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- Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig System.Net.Mail.Functional.Tests.runtimeconfig.json --depsfile System.Net.Mail.Functional.Tests.deps.json /home/REDACTED/.nuget/packages/microsoft.dotnet.xunitconsoleREDACTED/2.9.3-beta.25528.108/build/../tools/net/xunit.console.dll System.Net.Mail.Functional.Tests.dll -xml testResults.xml -nologo -notrait category=OuterLoop -notrait category=failing (dns block)
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- Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig System.Net.Mail.Functional.Tests.runtimeconfig.json --depsfile System.Net.Mail.Functional.Tests.deps.json /home/REDACTED/.nuget/packages/microsoft.dotnet.xunitconsoleREDACTED/2.9.3-beta.25528.108/build/../tools/net/xunit.console.dll System.Net.Mail.Functional.Tests.dll -xml testResults.xml -nologo -notrait category=OuterLoop -notrait category=failing (dns block)
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- Triggering command: /home/REDACTED/work/runtime/runtime/artifacts/bin/testhost/net10.0-linux-Debug-x64/dotnet exec --runtimeconfig System.Net.Mail.Functional.Tests.runtimeconfig.json --depsfile System.Net.Mail.Functional.Tests.deps.json /home/REDACTED/.nuget/packages/microsoft.dotnet.xunitconsoleREDACTED/2.9.3-beta.25528.108/build/../tools/net/xunit.console.dll System.Net.Mail.Functional.Tests.dll -xml testResults.xml -nologo -notrait category=OuterLoop -notrait category=failing (dns block)

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Original prompt

There is absolutely unnecessary unsafe code in SmtpReplyReaderFactory.cs in ProcessRead function, please file a PR to replace with just normal ReadOnlySpan memory access to make it memory safe.

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

…plyReaderFactory Co-authored-by: EgorBo <523221+EgorBo@users.noreply.github.com>

Co-authored-by: EgorBo <523221+EgorBo@users.noreply.github.com>

EgorBo · 2025-11-03T15:46:05Z

@MihuBot

xtqqczze

Codegen with !char.IsAsciiDigit((char)b) should be equivalent: sharplab.io

src/libraries/System.Net.Mail/src/System/Net/Mail/SmtpReplyReaderFactory.cs

Co-authored-by: xtqqczze <45661989+xtqqczze@users.noreply.github.com>

Copilot

Pull Request Overview

This PR refactors the ProcessRead method in SmtpReplyReaderFactory to eliminate unsafe pointer-based code in favor of safe, index-based buffer access. The logic remains functionally equivalent while improving code safety and maintainability.

Key Changes:

Replaced unsafe pointer arithmetic (ptr++, *ptr, etc.) with safe array indexing using an i counter
Removed the unsafe block and fixed statement that were previously required for pointer manipulation
Maintained the same state machine logic for parsing SMTP reply messages

src/libraries/System.Net.Mail/src/System/Net/Mail/SmtpReplyReaderFactory.cs

EgorBo · 2025-11-06T14:34:11Z

@stephentoub @MihaZupan is it fine to remove the unsafe from System.Net.Mail Smtp without perf benchmark, it's unclear to me how nanoseconds saved on bounds check can have an impact on it + SmptClient is effectively deprecated

EgorBo · 2025-11-06T14:35:17Z

I recommend reviewing it with "Hide whitespaces" option

MihaZupan

is it fine to remove the unsafe from System.Net.Mail Smtp without perf benchmark

Fine by me.

cc: @rzikm re: the changed validation for ASCII digits that were previously wrong and unreachable.

dotnet-policy-service · 2025-11-06T14:44:47Z

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wfurt · 2025-11-06T16:07:33Z

I think the perf is fine. But it still looks complicated to me. Basically it should be 3 digits + ASCII text. I would think there is better way than iterating though and keeping stated. (assuming we can handle the folding)

rzikm

LGTM, I agree that the logic could be simplified (not only here, but across the entire implementation), but I already touched many parts during the refactor that I didn't want to add another possible breaking point.

EgorBo · 2025-11-08T16:07:32Z

/ba-g deadletter

Initial plan

30d4e8a

Copilot AI assigned Copilot and EgorBo Nov 3, 2025

Copilot started work on behalf of EgorBo November 3, 2025 14:17 View session

EgorBo changed the title [WIP] There is absolutely unnecessary unsafe code in SmtpReplyReaderFactory.cs in ProcessRead function, please file a PR to replace with just normal ReadOnlySpan memory access to make it memory safe. [WIP] Remove unsafe code from SmtpReplyReaderFactory Nov 3, 2025

Copilot AI and others added 2 commits November 3, 2025 14:49

Replace unsafe pointer code with safe ReadOnlySpan indexing in SmtpRe…

14b429a

…plyReaderFactory Co-authored-by: EgorBo <523221+EgorBo@users.noreply.github.com>

Fix logic bug in digit validation (change && to ||)

ccbde35

Co-authored-by: EgorBo <523221+EgorBo@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Remove unsafe code from SmtpReplyReaderFactory~~ Remove unsafe code from SmtpReplyReaderFactory.ProcessRead Nov 3, 2025

Copilot finished work on behalf of EgorBo November 3, 2025 14:54

Copilot AI requested a review from EgorBo November 3, 2025 14:54

MihuBot mentioned this pull request Nov 3, 2025

[JitDiff X64] [Copilot] Remove unsafe code from SmtpReplyReaderFactory.Proce ... MihuBot/runtime-utils#1615

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xtqqczze reviewed Nov 3, 2025

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The Operation will be canceled. The next steps may not contain expected logs. dotnet/dnceng#3008

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Failed to install runtime_python_requirements #114924

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Co-authored-by: xtqqczze <45661989+xtqqczze@users.noreply.github.com>

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Copilot AI review requested due to automatic review settings November 4, 2025 14:45

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src/libraries/System.Net.Mail/src/System/Net/Mail/SmtpReplyReaderFactory.cs Show resolved Hide resolved

MihaZupan approved these changes Nov 6, 2025

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MihaZupan added this to the 11.0.0 milestone Nov 6, 2025

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MihaZupan added the reduce-unsafe label Nov 6, 2025

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EgorBo enabled auto-merge (squash) November 8, 2025 16:07

EgorBo merged commit a67d388 into main Nov 8, 2025
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EgorBo deleted the copilot/fix-9141961-210716005-fd74fffa-b923-44c0-9d8f-af4f306d56f1 branch November 8, 2025 16:07

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[main] Source code updates from dotnet/runtime dotnet/dotnet#3271

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Remove unsafe code from SmtpReplyReaderFactory.ProcessRead#121297

Remove unsafe code from SmtpReplyReaderFactory.ProcessRead#121297
EgorBo merged 4 commits intomainfrom
copilot/fix-9141961-210716005-fd74fffa-b923-44c0-9d8f-af4f306d56f1

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